In 148 patients admitted to hospital with acute cerebrovascular accidents (CVA), the levels of glycosylated haemoglobin (HbA1c) and blood glucose were measured to evaluate the effect of the duration and severity of hyperglycaemia on stroke outcome. Eighty-eight (59%) patients had clearly normal blood glucose and HbA1c concentrations (blood glucose less than 5.5 mmol l-1, HbA1c less than 8.6%). The remaining 60 patients were defined as hyperglycaemic. Nineteen (13%) had known diabetes, whereas in 23 (16%) hyperglycaemia was probably due to unrecognized diabetes. In 18 (12%) patients transient hyperglycaemia was observed. Recovery after CVA was best among normoglycaemic patients (good 45%, moderate 29%, poor 14%, fatal 12%) and poorest among diabetic patients (moderate 21%, poor 37%, fatal 42%). Fatal outcome in patients from the normoglycaemic group differed significantly from patients belonging to known diabetic and unrecognized diabetic groups (p less than 0.05), but was not different from that in patients with transient hyperglycaemia, who did however differ from both diagnosed and unrecognized diabetic patients (p less than 0.05). No significant differences were found between CVA outcome in the known diabetic and unrecognized diabetic groups.